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Clearing ARP on firewall restores connection

Suresh Varghese



I currently have an ASA5505 running Version 9.1(6)

The outside interface of the firewall is connected to ADSL router which in turn is connected to the internet

Every now and then...the connection drops and i am not able to ping the ADSL modem IP which is the gateway (default route) on the ASA

When i do a clear ARP on the starts working

I assume that this is not the ASA acting up but is an issue with the next hop device but how can i resolve this.


I would appreciate if anyone can shed some light in helping me sort this matter out.


many thanks in advance.




Florin Barhala
Frequent Contributor
Frequent Contributor
Let's tshoot this together.
First of all we have to find out the ARP entry that's causing trouble.

Can you post:
show run route
show nameif
show arp | i outside

Hello Florin,

Sorry for the delayed response, please find attached the output that you had requested for



What I am interested in as next step: next time you have this issue does the ARP entry looks the same as before :


outside 58ef.6809.a192 18


and of course after you clear ARP do you get same mac address?

Marius Gunnerud
VIP Advisor VIP Advisor
VIP Advisor

How often does this issue happen?

There is a bug related to proxy-arp that can cause this type of behavior.  Have a look

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Hi Marius

The issue happens whenever it feels like, no specific time of period.

As for the bug, we suspected the same and upgraded the firmware from version 8 to 9.1.6

Based on the table provided in the link by you, does it mean i have to upgrade to a more higher version.




You could also set up a capture on the ASA inside and outside interfaces when this is happening to see if traffic is actually being sent out the outside interface.  Also, before clearing the ARP table, check to make sure that the MAC to IP address mappings are correct for the default route.

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